AVR-Chat

Both SPI and TWI (I2C) are multi-drop. SPI requires a
separate enable (chip select) for each device so that could
mean a lot of "wires". Neither is designed for more than a
few meters.

For regular serial, RS422 is the one-talker, many listener
protocol and RS485 is the many-talk, many listen version
though they pretty much use the same hardware. National
Semiconductor, Linear Tech, and Maxim all have good app
notes on RS422/485. I have some experience and can help if
needed. These are good for a few km and use twisted pair.
They both tend to want linear topology rather than star
because of termination issues. Depending on the
transceiver, you can put 32 or more on a single system.
There is no predefined "protocol"; you have to make that up
for yourself.

CAN is like RS485 with a protocol built on top, as I
recall.

Jim


On Wed, 17 May 2006 11:02 +0100 (BST)
 "David Collier" <from_yahooAVRchat@dexdyne.com> wrote:
> 
> I want to string a load of simple slaves out along a
> serial bus.
> 
> Does anyone think I could implement a 1-wire slave using
> an ATtinyx5?
> 
> Yes I know it's patented.
> 
> Alternatively does anyone have a better suggestion? Would
> the I2C 
> look-alike mode do it for me? Anyone got any experience
> of such a thing, 
> or know where to scrounge the necessary code?
> 
> All suggestions gratefully received.
> 
> David
> 


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